Hitherto, various techniques have been proposed for incorporation into automatic double-side copying apparatuses that are used on an electrophotographic copying apparatus or on a laser printer or the like, and capable of subjecting recording sheet to each of one-side copying and double-side copying. Conventional automatic double-side recording apparatuses, in their image processing portion, record an image on one face of a recording sheet, thereby the recording sheet is temporarily stocked in an intermediate portion, and then, the sheet is refed into the image processing portion. Such automatic sheet recirculating/conveying apparatuses are disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 82247/1984, 114227/1984, and 2241/1985.
There has been developed a technique in regard with an image recording apparatus provided with image forming means that is capable of performing, not only the above-mentioned double-side copy mode where images are recorded on both faces of recording sheets, but a composite copy mode where images of plurality of document sheets are commonly copied onto one face of each recording sheet. One such a technique is disclosed, for example, in Japanese Patent O.P.I. Publication No. 123474/1987.
According to this patent, the technique is as follows: in the case of a composite copy mode for a single recording sheet, the recording sheet having been subjected to paper feeding, image-transferring, separating, and image-fixing is transported to a recirculating path for composite copying, and then, refed into an image forming portion based on a composite copy instruction entered from an operation part, thereby on the same face of the recording sheet is formed another copy image.
In the case of a double-side copy mode for one recording sheet, a recording sheet undergone one-side copying is temporarily delivered outside a copying apparatus by delivery rollers, and turned over, then refed into the image forming portion via the above-mentioned recirculating path, thereby a copy image is formed on the other face of the recording sheet.
In the case of a composite copy mode for a plurality of recording sheets, individual recording sheets undergone fixing are temporarily delivered outside, by the delivery rollers, outside a copying apparatus as controlled like in the case of the above-mentioned double-side copying operation for a single recording sheet, and then, by reverse rotation of the delivery rollers, the recording sheets are diverted from a certain point on the recirculating path, thereby these sheets are stored in the intermediate stacker. This sequence is maintained until all the sheets independently bearing a copied image on one face have been stored in the intermediate stacker. Then, based on a new copy instruction, the recording sheets are individually transported from the intermediate stacker, conveyed through the recirculating path, and fed into the image forming portion, thereby the second image is copied onto the individual recording sheets.
In the case of a double-side copy mode for a plurality of recording sheets, individual recording sheets are, as controlled like in the case of the above-mentioned composite copy mode for a single sheet, transported from a fixing unit to a certain point in the recirculating path, where diverted and then stored in the intermediate stacker. The operation onwards is identical with that of the above-mentioned composite copy mode.
As described above, a conventional recording sheet conveyance apparatus used on an image recording system, and that is capable of performing automatic double-side/composite copy modes has a complicated recording sheet conveyance path for double-side and composite recording modes, and, therefore, such an apparatus is disadvantageous in that such a path incurs complicated constitution, operation, and controlling.
In a double-side copy mode or composite copy mode, and when recording sheets of various sizes independently bearing an image on one face are temporarily stored in an intermediate stacker, some of the leading edges fail to reach the stopper face of the intermediate stacker because of different lengths of the sheets, and, the recording sheets are therefore misaligned with each other. As a result, there can occur a problem of misfed sheet, or misoriented recorded image, or the like when the recording sheets are refed to an image forming portion and subjected to double-side or composite copy operation.